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Discussion Starter #1
Hi all,
I just got handed a package deal of vehicles, one of which is a 1995 RamVan conversion with 5.2L and 3-spd O/D auto trans. It was from a friend who never really used it, and so I don't know much of the history other than the 169k mi on the clock.
It will not restart for 1-1.5 hours after being driven. It cranks but will not fire. A shot of starter fluid shows that there is spark, but apparently no fuel (very hard to hear the fuel pump prime, but I'm pretty sure I do not hear it when it is refusing to start). After researching on here and other forums the ASD and fuel pump relays sounded like a likely culprit. I replaced them and the problem persists.
Interestingly, if you shut it off and try to start it within a few minutes, it starts. It's only if you let it sit for 10+ minutes that it no longer wants to start. Something electric must be causing the fuel to not deliver (most likely the fuel pump not being told to cycle).
I have a '91 B250 with 5.2L but unfortunately the service manual I have does not cover the sequential-port injected versions of this van, just carb and TBI vans. I have more time than money currently, so when a manul arrives in the mail I will be trying to troubleshoot. If the ASD/ fuel pump relays are not the problem, what do you all think a logical order would be in checking? I'm hoping tomorrow to snag my neighbor to cylce the key so I can certify the relays are clicking (so hard to tell by just sticking my head out the window). From there I will likely need the manual to start ringing wires and checking things.
Oh, also, no check engine light. I don't have a reader and it does not do the key-cycle like my '91, so I assume it is OBD-II and needs a reader. The CEL does physically work (no one pulled the bulb or anything), but it has not come on to indicate a problem.
It's going to be a few days till I get the manual in the mail so I am trying to plan an order of operations to get as much tested in the 1-1.5 hours it is acting up after shutdown.
Thanks,
Johnny
 

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Given that something appears to be failing when it is heat soaked and you still have spark, my first suspicion would be in the distributor as it provides the signal to fire the injectors via a hall effect.
 

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If it has a crank position sensor, that can also be heat sensitive. The distributor hall effect or crank sensor may not throw a fault code.
Best diagnosis would be a scan tool that can see what's missing here, but a common OBD II scanner won't work on a '95. A scope or analog voltmeter on the crank or cam (distributor) signal wire to the PCM while cranking might see which sensor is dead.
The crank and cam sensors are powered by an 8 volt supply from the PCM and the resulting signal is a square wave out of the sensor while cranking/running.
 

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Discussion Starter #4
I don't understand why it needs to be an analog voltmeter? What am I supposed to be looking for when testing the distributor or crank sensor? It's not just a case of the sensor sending a signal or not?
-Johnny
 

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The pulses from the sensor will be too rapid to see on a digital meter sampling rate. All you will see is numbers jumping all over the place.
The analog meter will provide you with needle-sweeps that will actually show you that it is pulsing rhythmically.
 

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Discussion Starter #6
Ah, got ya. The last time I was testing a distributor for signal I just assumed the jumping numbers meant I was getting a good signal.
I wasn't able to get anything done on the van today, and tomorrow doesn't look much better. Looks like I need to search for someone with an analog voltmeter anyway, though I'll probably try first with my digital meter... no signal at all would be a give away as to the problem.
Will post results in a few days once I have gotten some time with it.
Thanks,
-Johnny
 

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Discussion Starter #7
How is this for interesting luck?
My neighbor got a 1995 Ram Van Conversion with 5.2L motor to do some work on. Cracked block, so the whole motor is out of it.
I ask to borrow the Hall effect pick up out of his distributor.
After idling it for about 20min I shut it off and try to restart... only cranks. Spark (starting fluid down the intake to verify) but no fuel (no 12V signal to one of the injector leads while cranking).
Since I've now replaced the Hall effect and the ASD/fuel pump relays, my eyes turn to the computer on the firewall. Well, since I have a parts car just sitting accross the street, we plug his computer in.
Starts right up, no problem. Thinking this solved the problem, I plug my computer back up and it fires right up too.
Well, maybe it cooled off enough??? So I idle it another 20min with the doghouse back on and hood closed. Fired ride up immediately after shut down, and 5min later. What the hell? Now I'm worried since the problem went away, but it's not "fixed" as far as I'm concerned. I didn't notice any corrosion that I could have knocked loose in the connection to the computer... it all looks clean as the day it was built in the computer and the wiring connector.
Baffled. I have to put this thing on the road now, and I am swapping the tow receiver from my other van onto this one, so there is no turning back. Here's hoping.
b-z-
 

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im having a very similiar problem with my 89 B250 318 tbi, but it seems like more fuel related to me, like a drop in pressure after running for aw hile, mine will start if yiu pump the gas while cranking but starts cold rite up no problems. any tips you have an 91 with tbi rite?
 

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Discussion Starter #9
Yes '91 TBI 5.2L.
T-off somewhere and put a fuel pressure gauge on it. See what the difference is cold and hot. That's where I'd start. If there is a difference in throttle response I'd be more interested in the injector, but if it's only as difficulty in starting when hot I'd want to know the fuel pressure. I have no direct experience with that problem though. Sometimes when cold I would get a big hesitation while driving if I opened the throttle, but it didn't always do it and it went away when warm so I never concerned myself with it.
b-z-


I should clarify though, the problem in this thread is for my '95 MFI van. The above thread about a hesitation and T-ing off the line I was referencing my '91 TBI van.
I own two.
b-z-
 

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Discussion Starter #10
Ok I lied, the problem is back. So, up to this point, I replaced the ASD relay/fuel pump realy combo, I swapped out the hall effect pickup in the coil for a known good one, and I swapped the computer for a known good one. When I swapped the computer the vsn fired up, but when I plugged my computer back in, it also fired up. I assume it was coincidence.

I was just doing a cooling flush on the van and it will not restart now. I tried unplugging/replugging the computer but no luck. I can hear the realy kick on when I flip the key to "on" (I assume that's the ASD relay?) and after cranking the engine I can hear the relay click again after a few seconds (again, I assume it's the ASD relay). It only seems to do this when hot. Hoping it was the computer, I've had a box fan blowing on it for 10min but no dice. I'm stuck on a logical next step other than tracing the fuel pump wires and making certain it is getting 12V when cranking. It gets spark during this because a shot of starting fluid results in combustion (the engine tried to start), so it has to be fuel-delivery related. And good guesses on a logical flow of things to check?

I gotta admit, this is a lot harder for me than the motorcycles I usually work on; everything is out of reach. where is an easy spot to check for 12V to the fuel pump where you can read the multimeter and crank the engine without an assistant?
Thanks,
-John
 

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Did you ever get a code reader on it? If not, take it to an auto parts store and have them retrieve the codes for free.

I wouldn't outright blame the computer, as something else could cool down in the time it took to swap the computer out. The crankshaft position sensor is still a suspect, and I wouldn't rule out the ignition coil, either, as it sits right near the hot exhaust manifold. I would do more diagnosis first, and getting the codes will be important.

Try again with the key method. Your van should be OBDI and this should work. Does the check engine light work at all, for instance, when you turn the ignition to ON just once, without cranking?
 

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Discussion Starter #12
CEL does work yes. I noticed they changed it from amber to red between my '91 and this '95. I never did get codes retrieved. I'll have to ask an autoparts store; a year or two ago I saw signs at one saying they couldn't read codes because of some new state law, but I can't imagine that would slip by without an uproar. I thought it would be OBD-I also.

Ah ha! I went out and tried it again. You have to cycle the key slowly compared to my '91 for some reason. Alas, there is no code. only CODE 12 (from me disconnecting the battery) http://www.allpar.com/fix/codes/faults/code12.html and 55 of course. I'm not dead set on the computer either, but this is very hard to troubleshoot because it only does it sometimes and it only does it for a random amount of time before cooling off. In fact, after writing that last post, I went out and pulled the doghouse off to try and find a fuel injector wire to test for signal and right after I got it off I checked... the damn thing started. Having swapped the pick-up coil out of the distributor and still having the problem rules it out, but I agree there is the coil and perhaps another relay I'm missing. Is there a 2nd crank sensore anywhere? Is there a cam sensor (besides the pick-up coil)? I guess I will be reading the manual tonight.
-John
 

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Probably a stupid question, but I'm going to ask it anyway, because I don't know. Would a faulty coolant temperature sensor cause the no start when it gets hot? IC, Bob L., either of you guys know?
 

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Probably not. If it opens, there is still a 10K resistor in the circuit, I believe, it would react as if it were seeing about a 30-40F temperature. It might flood a little, but it would be obvious from the smell. If it shorted, it would trip the Check Engine light.
 

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I'm guessing you don't have a No Bus displayed when it won't start since you don't mention it. Still might be worth checking the 5V reference at any one of your sensors when its acting up. I initial thought mine was a fuel issue the way it acted, but it was all computer related in the end. Some of the questionable sensors I replaced may have been what cooked the computer in the first place.

You asked about fuel pump access. There should be a 4 pin connector just forward of the fuel tank that you can check the pump without dropping the tank. At least narrow it down to pump and the short harness directly attached to it...
 

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Discussion Starter #16
OK, thanks everyone. I will write out a logical flow of tests and locate a means to test them. I am swapping the radiator out today so it will be a perfect time to get the engine bay heat-soaked after the install. Hopefully it gives me the no-start problem and I can get to work testing things quickly before it cools down. I have a race in Utah (700mi away) Aug 30 and I really don't want to leave it running during fuel stops and meals out of fear... it's just not practical. However, the tow hitch is already swapped over from my '91 van and that means the '95 has it's marching orders come August.

On the "No Bus", is that a fault code? I am not sure I have ever checked codes while it was in a no-start condition, but the fault should be stored, yes? I onlt get 12 and 55, but come to think of it, I disconnected the battery when I unplugged/re-plugged the computer, so I would have erased any codes. Unless the codes would have tripped during my cranking attempts afterward, there probably wouldn't be any codes to display.

On the coolant sensor, on my '91 TBI 5.2L I had a coolant temp sensor go out when hot and- as you said- the engine went rich, throwing whichever code is the "takes too long to warm up" code, and would stutter to a halt, unable to take throttle and idling unevenly. After 10-20min of cooling it fired up and acted normal, until the next hill. Swapping the coolant sensor appears to have stopped the problem, though it has returned now, years later.

Cheers,
-John
 

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If the van has a digital odometer, the no bus message may be dispayed there.
 

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Discussion Starter #18
Nope, the odometer is not LCD.

I broke a tranny cooler line swapping the radiator. Will install a replacement today and see what I can figure out.
-John
 

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Discussion Starter #19
Well, after 2 days of jimmy-ing around with the freakin' trans cooler line I was finally able to fire up the ol' girl and put some heat into it. Like clockwork, after shutting it down and immediately attempting to restart, if fired up no drama.

After less than 5 min I tried to fire it up and it was the usual no-start condition. Cranking but no fire. First thing first I go to check the codes... there is no check engine light. Not a blip. Not in "ON", not during or after cranking, not halfway between ON and START. The parking brake, ABS, and airbag light also did not come on, but I think that is unrelated. I replaced some of the backlighting for the instruments and probably did not plug that back in when installing the dash.

Anyway, I throw the ol' box fan on the engine and aim it basically at the computer, then kept coming back every 3-5 minutes to see if the check engine light (CEL) will come on. After about 15min it comes on, and the engine starts. No new codes have tripped. I still have 12 and 55.

I'm highly suspect of the computer now. That is couldn't find a fault or turn on the CEL makes me think it's out to lunch when it gets hot. Strangely, it does not cut out while driving though; I have shut it off and immediately tried to restart it in the past and it would not start. It's only after shutting off that the problem appears. It's not checking out while the engine is running, only when it's off.

Before I run out and look for a computer, does anyone have any last minute thoughts/checks I should try? I didn't even boter trying to test the fuel pump just now because with no CEL I was stopped in my tracks, focusing on that problem. I certainly need this problem gone by Aug 28, when the team hits the road again for Utah.
-John
 

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Discussion Starter #20
Well, the crank sensor tests in the book involve hooking up the scan tool and reading the voltage. The other checks to verify with a multimeter are fairly confusing. I figured them out, but one of them was out of spec. However the instructions were along the line of "if it's less than 5v, repair the wiring, if it's more than 5v, replace the sensor. I had really high readings. I don't even remember the numer, tens of thousands of ohms. I didn't get why it had to be exactly 5ohms or something was wrong.

I tried on my digital mutimeter to read the power wire to the sensor. It showed 3.6V with key on, then 2.0v while cranking. The ground wire from the ECU to the sensor is good, and so is the power wire. That's about the best I know to do without the scan tool. A sensor is only $36 with free shipping, and that's cheaper than the tool. Guess I will have a go at that before a computer (although I've found some really good prices on used computers so far).

Hate to just buy a sensor and hope it works kinda thing, but buying the scan tool... I dunno. It seems like none of them work right. I've only used one a handful of times (on Ford and GM, not Mopar) and they would trhow the wackiest codes at you and fail to perform tests they were supposed to be able to do.
-John
 
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